1. Technical Field
The present disclosure relates to a nonaqueous electrolyte secondary battery.
2. Description of the Related Art
Japanese Unexamined Patent Application Publication No. 2000-149924 aiming to improve safety in the event of overcharging discloses a nonaqueous electrolyte secondary battery in which an intermediate layer mainly composed of graphite is disposed between a positive electrode mix layer and a positive electrode current collector. Japanese Unexamined Patent Application Publication No. 2009-16106 discloses a nonaqueous electrolyte secondary battery in which a flame retardant is added to a positive electrode mix layer to suppress thermal runaway reactions.
According to the technologies disclosed in these patent documents, the safety of batteries may be improved. However, with respect to internal short-circuiting caused by nail penetration or the like, the battery disclosed in Japanese Unexamined Patent Application Publication No. 2000-149924 may need a further improvement. In particular, high-energy-density batteries generate a large quantity of heat in the event of internal short-circuiting and thus suppressing heat generation and enhancing safety are desirable for such batteries. Adding a flame retardant to a mix layer, as in the battery disclosed in Japanese Unexamined Patent Application Publication No. 2009-16106, degrades output characteristics.